Paging message processing

Abstract: A mobile station, i.e., mobile phone included in a cellular telephone system processes paging messages using a dual-port RAM memory connected between a signal processor (DSP) and a microprocessor (MCU). The paging message received and coded by the signal processor is transferred to the RAM memory, the identity number contained by the paging message is compared with the identity number of the microprocessor at the same time in the signal processor and only when they are congruent, the microprocessor is activated through a separate interrupt line. Because most paging messages are either empty messages or intended for other mobile stations, the microprocessor (MCU) can remain on as low a power level as possible during the paging of messages while the mobile station is in the stand-by state.

Description: The present invention relates to an apparatus and method for processing paging messages received by portable devices such as radio telephones or message pages. It is a well known aim for designers of portable devices to minimize the power consumption of such devices, e.g. radio telephones, in order to increase the interval between the charging and replacing of the batteries for the portable devices. Additionally, the likelihood of the portable device ceasing operation during a working cycle is reduced if power consumption is minimized. Therefore, portable devices, particularly radio telephones, are designed so that different power-consuming parts can be shut off when not required so that only the necessary parts required to "activate" the portable device are switched on. In a portable communication system, the portable devices are paged by radio transmitted paging messages. The so-called paging messages are transmitted using paging channels of the communication system to the portable devices, e.g. cellular telephone, inside a given cell in different systems. The cellular telephone recognizes, on the basis of these messages, whether or not there is an incoming call for that cellular telephone i.e., whether certain parts of the cellular telephone should be activated. These paging messages are typically transmitted, for example, as signal blocks, signal bursts or as an FSK-modulation bit stream, using a continuous carrier wave. The particular implementation depends on the communication system. Typically, such communication systems have discontinuous reception (DRX), i.e., parts of the cellular telephone are switched off between paging messages and also during paging messages. This is the case when the cellular telephone is in the so-called idle state (stand-by). In the stand-by state the power consumption of cellular telephones is mainly due to the receiving and handling of paging messages. Generally the power consumption is reduced by the power being switched off between paging message blocks, but power consumption should be minimized also during paging message blocks or bursts. In known digital cellular telephones, for example, the reception of paging messages is carried out in the following manner. Paging messages are received and decoded in a digital signal processor (DSP) and the decoded bits are subsequently analyzed in the microprocessor (MCU). A parallel or serial bus is generally provided between the microprocessor and the digital signal processor. A drawback in this process is that the whole reception chain is switched on during or after the reception of a paging message block. Additionally, the majority of paging messages do not require any activity from the cellular telephone because they are either so-called empty messages or paging messages for other cellular telephones. A known improvement on the above method is one where relevant paging messages are partly detected in the signal processor DSP and any blocks which require activity are then forwarded to the microprocessor for full processing. A drawback here is that because the signal processor has to transmit the information to the microprocessor, this information is written into the memory twice, the first time into the memory of the DSP and the second time the same information is written into the memory of the MCU. Therefore, both the microprocessor and the signal processor have to be switched on or they have to use a higher clock frequency for a longer period of time if the microprocessor is one which does not have a halt mode. Another disadvantage is that the MCU and/or its peripheral interface circuits (serial/parallel ports, DMA controller, etc.) have to be activated in order to transfer the paging information into the memory of the MCU. The MCU can start processing the data only after the whole message has been transferred to the RAM area for the received messages. The characteristic features of the method and apparatus according to the invention are recited in the characterising portions of claims 1 and 5 respectively. A method and apparatus in accordance with the present invention has the advantage that unnecessary data transmission between the signal processor and microprocessor is reduced thereby reducing power consumption and increasing battery life. Additionally, the processing time of the signals is reduced. The dual port RAM is a fast device and thus the signal processor can fully activate microprocessor at the very moment the data to be processed is available. The invention is described in detail in the following, by way of example only, and with reference to the accompanying drawings in which: Figure 1 shows a circuit diagram in accordance with the invention; and Figure 2 shows a flowchart of the steps taken in accordance with the invention. A paging message transmitted by a base station on a paging channel is received in the RF section of a cellular telephone, after which the detected signal is transferred to the digital signal processor DSP illustrated in Figure 1. The paging message contains the identity number of a cellular telephone. Paging messages are not received continuously and generally the pause between the messages is longer than the actual messages. For instance, in the GSM system, a paging message block is transmitted at intervals of 0.5 - 2 seconds while the length of the actual block is about 20 milliseconds (the block contains four bursts of 0.577 ms each, where the gap between each burst is 4.615 ms). If there is no need to search for or page a cellular telephone, an empty frame of a predetermined type can be used. When the cellular telephone is in stand-by, it has to receive paging messages at predetermined moments and the receiving circuit can be switched off between these moments either partially or completely. The paging message is received in the RF section of the cellular telephone and then sent to the signal processor DSP where it is decoded and transferred to the dual-port RAM memory. The microprocessor is activated only when needed. The operation of apparatus in accordance with the invention is shown in Figure 2. At step 201, the cellular telephone is in standby mode, and at 202 a paging message is expected and the MCU is in a lower power mode. At 203 the MCU transmits the identifier of the mobile station (for instance, identity number TMSI or IMSI) or a part thereof to the DSP. Then, the DSP receives and decodes the paging message block 204 and places it in the dual-port RAM memory 205. The identifier received via the RF part from the outside is compared in the DSP with the identifier obtained internally from the MCU at step 206. If the numbers are congruent, the DSP activates the MCU through the interrupt and the MCU further directs the other necessary parts of the mobile station to be switched on 207, 201 and if the identifiers are not congruent, the DSP does not activate the MCU, and the MCU remains on as low a power level as possible in its standby mode. After having completed whatever functions are necessary having been fully activated, the MCU returns to its standby mode. The identity number can be, for instance, in the GSM system a so-called IMSI (International Mobile Subscriber Identity) or a TMSI (Temporary Mobile Subscriber Identity). However, independent of whether the system in question is digital or analog, and in the case of digital systems whether it is GSM or some other system, it is typical that some kind of an identifier of the mobile station comes along with the paging message. It can be further stated here that if the paging message contains a so-called empty message (for instance, a filler frame) the DSP verifies this and ignores the block. In a cellular telephone operating in accordance with the invention, the MCU can be on a low power level until it receives an interrupt signal from the DSP. The interrupt signal can be transmitted to the MCU by other means providing the DSP has first compared the identifiers or parts thereof. The invention can be applied both in digital and analog cellular telephone systems. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. For example, this dual-port RAM can be a separate circuit or it can constitute a part of any IC of the cellular phone, and dual-port RAM memory can also be used to transfer other messages between the MCU and the DSP. The scope of the present disclosure includes any novel feature or combination of features disclosed therein either explicitly or implicitly or any generalisation thereof irrespective of whether or not it relates to the claimed invention or mitigates any or all of the problems addressed by the present invention. The applicant hereby gives notice that new claims may be formulated to such features during prosecution of this application or of any such further application derived therefrom.

Claims: A method for processing paging messages, characterised in that it comprises the steps of: transmitting (203) from a microprocessor (MCU) a first identity number to a signal processor (DSP), decoding (204) a received paging message at the signal processor (DSP), writing (205) the decoded received paging message into a dual port RAM memory (RAM), after the decoded received paging message has been written into the dual port RAM memory comparing (206) a second identity number contained within the decoded received paging message with the first identity number at the signal processor (DSP), and if the second identity number is found to correspond (207) to the first identity number, fully activating (208) the microprocessor (MCU) from a partially activated state and processing data contained in the decoded received paging message that is stored in the dual port RAM memory (RAM), by the microprocessor (MCU). A method according to claim 1, characterised in that the step of fully activating (208) the microprocessor (MCU) from a partially activated state involves the signal processor (DSP) using an interrupt signal to fully activate the microprocessor (MCU). A method according to claim 1 or 2, characterised in that as a part of the method empty paging messages are identified by the signal processor (DSP) and are not processed by the microprocessor (MCU). A method according to any preceding claim, characterised in that the paging message is received at intervals as a signal cluster. Apparatus for processing paging messages comprising: a signal processor (DSP) and a microprocessor (MCU); characterised in that : it comprises a joint dual-port RAM memory (RAM) coupled to the signal processor (DSP) and the microprocessor (MCU), the signal processor (DSP) comprises means for writing the decoded received paging message into said dual port RAM memory (RAM), means for comparing, an identity after a decoded received paging message has been written into the dual port RAM memory number contained in the received and decoded paging message with a first identity number obtained from the microprocessor (MCU), and control means for fully activating the microprocessor (MCU) from a partially activated state if the first identity number is found to correspond to the identity number contained in the paging message, and the microprocessor is arranged to, as a response to an activating signal from said control means, process data contained in the decoded received paging message that is stored in the dual port RAM memory (RAM). Apparatus according to claim 5, characterised in that the dual-port RAM memory (RAM) is adapted to transmit parallel signals between the signal processor (DSP) and the microprocessor (MCU) and to receive messages processed by the signal processor (DSP). Apparatus according to claim 5 or 6, characterised in that the microprocessor (MCU) is arranged to be fully activated by an interrupt signal from the signal processor (DSP). Apparatus according to any of claims 5 to 7, characterised in that the dual-port RAM memory (RAM) is a circuit separate from the signal processor (DSP) and the microprocessor (MCU). Apparatus according to any of claims 5 to 7, characterised in that the dual-port RAM memory (RAM) is integral with one of the signal processor (DSP) and the microprocessor (MCU). Apparatus according to any of claims 5 to 9, characterised in that it is arranged to receive paging messages periodically as a signal cluster.

Inventors: HEIKKILA ILKKA, JOKIMIES MATTI, HEIKKILA, ILKKA, JOKIMIES, MATTI
Applicants: NOKIA CORP, NOKIA CORPORATION
Application year: 1994
Main classification: H04Q7
IPC codes: H04W52